Author

Abstract

Polymer gels have been effectively applied to extend the productive life of mature oilfields by mitigating water production and enabling the recovery of bypassed oil reserves. A key component for a successful conformance improvement treatment is the identification of the most appropriate gel technology for a targeted reservoir. Gel projects are capital sensitive and involve high degree of risk; therefore, it is crucial to select a proper gel technology and provide an optimized design project. This paper presents the first generalized comprehensive selection system for injection well gel technologies based on the comparative analyses of the characteristics of conformance problems in gel field projects. 111 field trials of three in-situ gel systems including bulk gels, colloidal dispersion gels, and weak gels were summarized from 1978 to 2015. First, reservoir/fluids characteristics, diagnosis indicators used in the evaluation of drive-fluid channeling strength, and treatment operational parameters were summarized. Then, problem zone volumes were estimated using a design rule of thumb and the problem development status was indicated using some production-related parameters. Finally, all characteristics of conformance problems were compared for different gel systems to identify factors implicitly used in the nomination of gel technologies in the field projects. We recognized that gel selection process starts by matching characteristics of conformance problems with technical specifications and mechanisms of the gel systems. Then, the initial candidate technology is confirmed by screening criteria to ensure gel system compatibilities with reservoir and injected fluids. We identified that the most influential characteristics in the selection process are drive-fluid channeling strength, volume of problem zone, problem development status, existence of cross-flow, and the nature of the required solution whether it depends on gel strength or volume. It was recognized that the existence of crossflow or high oil saturation in the offending zones turns a limited conformance problem into a large volume issue that needs the application of the flood-size treating technologies. For these situations, current oil saturation in the problem zones is the key factor rather than oil saturation in the less conductive zones because it is guaranteed by the high reservoir permeability heterogeneities. In addition, the problem development status does not only affect the selection of a gel system, but also its design parameters such as polymer concentration. The novelty of the new gel selection system is in its utilization of standardized general parameters and provision of distinct parameter cut-offs for each gel technology.